Forwards URL parameters in WMS cascading

[elzouavo]

MapServer allows "Changing map file parameters via a form or a URL" (cf. http://mapserver.org/cgi/controls.html#changing-map-file-parameters-via-a-form-or-a-url).
WMS 1.3 standard specifies the pixel width : 0.28 mm. That value gives a resolution of 25.4/0.28 = 90.71 dpi approximately.
Common GIS softwares works with a resolution of 96 dpi.
Popular WMS servers extend WMS service with dpi parameters:

• MapServer with MAP_RESOLUTION=value ;
• GeoServer with FORMAT_OPTIONS=dpi:value ;
• QGIS Server with DPI=value.

For example, QGIS adds all those parameters at the end of WMS/GetMap queries.

I've tested with MapServer 6.2 and it works fine, but...
When MapServer is also used as WMS client, it doesn't cascade those parameters.

At the present time for a layer named Layer1 :

• MapServer, as WMS Server, takes into account MAP_RESOLUTION via an URL
• If Layer1 uses MapServer as WMS client (cascade WMS), MAP_RESOLUTION (and the others dpi parameter) are lost.

Is it possible to improve MapServer to forward those 3 parameters in WMS cascades.

Regards

[jratike80]

Hi,

I think that you can do that already if you know the brand of the remote WMS because the extra parameters can be included in the server ur and runtime substitution can be used in CONNECTION http://mapserver.org/cgi/runsub.html. Therefore it migh be possible to use
CONNECTION "http://demo.mapserver.org/cgi-bin/wms?vendor_parameter1=%MAP_RESOLUTION%"

However, I am not sure if it really works because MAP_RESOLUTION is a known keyword for Mapserver and I do not know if is can be used as a variable. You may have a try. But for sure you can use a hardcoded resolution parameter in the server URL if it is not so important for you to let user to adjust the resolution on the fly.

[elzouavo]

Hi,

Thank you for your reply. I tried the proposed solution. MapServer is being used as a client and server WMS. I added &MAP_RESOLUTION =%MAP_RESOLUTION% to the layer CONNECTION but it does not work.
I've read the documentation and I saw FILTER VALIDATION.
So I've had "MAP_RESOLUTION" "^[0-9]{1,3}$" to the VALIDATION block into the WEB block and "all's well that ends well !".
It works !!!!!!!

Thanks a lot
Regards